Metabolism Flashcards | Quizlet

The three key enzymes catalyzing the three essentially irreversible reactions of glycolysis are, in order: a/ citrate synthase, hexokinase, pyruvate carboxylase b/ pyruvate kinase, phosphofructokinase, protein kinase A c/ protein kinase A (PKA), PFK, hexokinase b/ most of the time in most of the body's tissues c/ after meals in the liver and most of the time in most tissues d/ most of the time in the liver and during strenuous exercise in muscle tissue e/ after meals in the liver and most tissues When blood glucose is low, as during fasting or exercise, glycogen in muscle is broken down by the enzyme ___ to produce ___, which is converted to ___for glycolysis. a/ glucose synthase glucose 6-phosphate, glucose 1-phosphate b/ glycogen phosphorylase, glucose 6P, glucose 1P c/ glycogen phosphorylase, glucose 1P, PEP d/ glycogen carboxylase, glucose, glucose 6P e/ glycogen phosphorylase, glucose 1P, glucose 6P Aside from allosteric regulation by glucose 6-phosphate (glucose 6P), glycogen synthesis and breakdown in muscle is regulated by intracellular signaling pathways controlled by insulin, adrenalin and glucagon. Insulin ___ glucose uptake by tissues, to be stored as glycogen if there
Continue
reading >>

Popular Questions

Doug Freyburger

Others have mentioned the chemical details that lead to limits. That's only one side of the story. The other side is redundancy in energy production. Ketones can be used in anaerobic energy production. It's not as efficient but it is faster. There are times when fast beats efficient so redundancy gets selected for.

Anand R

Acetyl CoA can’t be circulated for two reasons: it’s a high energy compound and it’s labile. So it’s not a stable form for circulation to tissues. Also acetyl coA cannot cross cell membrane.Ketone bodies are an alternate fuel source. More importantly, they are water soluble analogs of fatty acids. This is important since, during starvation there is fat breakdown and excess fatty acids circulate in blood. However, fatty acids cannot be used by brain as fuel since, they cannot cross the blood brain barrier. Liver by producing ketone bodies helps brain cells during starvation.

Also, these ketone bodies, as such, can be used by other tissues as well. There by other tissues refrain from using glucose. Hence, ketone bodies have a glucose-sparing effect. This glucose will be available for tissues like brain and red cells for use.

Barry Gehm

It’s because oxaloacetate is needed to metabolize acetyl-CoA (first step in the Krebs cycle is the reaction of acetyl-CoA with oxaloacetate) and is also needed (and used up) in gluconeogenesis (the production of glucose from amino acids and other small molecules, but NOT from acetyl groups or fatty acids). The liver is primarily responsible for gluconeogenesis, and if it uses up oxaloacetate on that, acetyl-CoA builds up and ties up all the coenzyme A in acetylated form. In order to alleviate this, the liver converts the acetyl-CoA into ketone bodies, and releases them into the blood. These, as the book says, are taken up by other tissues (such as brain and muscle) and converted back into acetyl-CoA. A key point is that these cells can use the acetyl-CoA because they are not depleted in oxaloacetate because they do not carry out gluconeogenesis.

Moof's Medical Biochemistry Video Course: http://moof-university.thinkific.com/... In this video, I describe how Ketone Bodies are oxidized for energy. The liver makes ketone bodies that travel through the blood to extrahepatic tissues, where they are oxidized in the mitochondrial matrix to give energy. The pathway begins with D--Hydroxybutyrate, as it is oxidized to Acetoacetate by the same D--Hydroxybutyrate Dehydrogenase reaction (except in reverse). The Acetoacetate is then activated to Acetoacetyl-CoA by -Ketoacyl-CoA Transferase (also known as Thiophorase); this second step takes a Coenzyme A from Succinyl-CoA (an intermediate of the Krebs Cycle). The Acetoacetyl-CoA is then cleaved into two Acetyl-CoA molecules that can go through the Krebs Cycle to be oxidized, resulting in energy that cell can use. Ultimately, the liver is basically sending Acetyl-CoA that it isnt metabolizing to other tissues (by way of Ketone Bodies in the blood) so that those other tissues can utilize the Acetyl-CoA. However, sometimes, the extrahepatic tissues do not oxidize the ketone bodies rapidly enough to keep up with the pace at which they are arriving from the blood. This is a problem described

Ketone Bodies Metabolic Pathwayrat Genome Database

zed in the citrate cycle pathway during starvation, its conversion to ketone bodies and export from the liver permits continued operation of the fatty acid beta degradation pathway. To form ketone bodies, two molecules of acetyl-CoA are condensed by acetyl-CoA C-acetyltransferase (Acat1) into acetoacetyl-CoA. Several pathway enzymes have mitochondrial and cytosolic isoforms; the former, predominantly operant enzymes are shown in the forefront in the diagram. Another molecule of acetyl-CoA is then condensed with acetoacetyl-CoA by 3-hydroxy-3-methylglutaryl-CoA synthase (Hmgcs2) to form 3-hydroxy-3-methylglutaryl-CoA. This is cleaved by 3-hydroxy-3-methylglutaryl-CoA lyase to generate acetyl-CoA and acetoacetate. The acetoacetate is reduced reversibly by 3-hydroxybutyrate dehydrogenase (Bdh1) to yield 3-hydroxybutyrate, or is decarboxylated spontaneously or via acetoacetate decarboxylase (Adc) to generate acetone. To date, the Adc gene has only been cloned from prokaryotes, although enzyme activity has been studied in mammals (see PMID: 12726989 ). Outside the liver, 3-hydroxybutyrate is oxidized back to acetoacetate (Bdh1), which is then converted to acetoacetyl-CoA by 3-oxoacid C
Continue
reading >>

Popular Questions

Doug Freyburger

Others have mentioned the chemical details that lead to limits. That's only one side of the story. The other side is redundancy in energy production. Ketones can be used in anaerobic energy production. It's not as efficient but it is faster. There are times when fast beats efficient so redundancy gets selected for.

Anand R

Acetyl CoA can’t be circulated for two reasons: it’s a high energy compound and it’s labile. So it’s not a stable form for circulation to tissues. Also acetyl coA cannot cross cell membrane.Ketone bodies are an alternate fuel source. More importantly, they are water soluble analogs of fatty acids. This is important since, during starvation there is fat breakdown and excess fatty acids circulate in blood. However, fatty acids cannot be used by brain as fuel since, they cannot cross the blood brain barrier. Liver by producing ketone bodies helps brain cells during starvation.

Also, these ketone bodies, as such, can be used by other tissues as well. There by other tissues refrain from using glucose. Hence, ketone bodies have a glucose-sparing effect. This glucose will be available for tissues like brain and red cells for use.

Barry Gehm

It’s because oxaloacetate is needed to metabolize acetyl-CoA (first step in the Krebs cycle is the reaction of acetyl-CoA with oxaloacetate) and is also needed (and used up) in gluconeogenesis (the production of glucose from amino acids and other small molecules, but NOT from acetyl groups or fatty acids). The liver is primarily responsible for gluconeogenesis, and if it uses up oxaloacetate on that, acetyl-CoA builds up and ties up all the coenzyme A in acetylated form. In order to alleviate this, the liver converts the acetyl-CoA into ketone bodies, and releases them into the blood. These, as the book says, are taken up by other tissues (such as brain and muscle) and converted back into acetyl-CoA. A key point is that these cells can use the acetyl-CoA because they are not depleted in oxaloacetate because they do not carry out gluconeogenesis.

Does Fat Convert To Glucose In The Body?

Your body is an amazing machine that is able to extract energy from just about anything you eat. While glucose is your body's preferred energy source, you can't convert fat into glucose for energy; instead, fatty acids or ketones are used to supply your body with energy from fat. Video of the Day Fat is a concentrated source of energy, and it generally supplies about half the energy you burn daily. During digestion and metabolism, the fat in the food you eat is broken down into fatty acids and glycerol, which are emulsified and absorbed into your blood stream. While some tissues -- including your muscles -- can use fatty acids for energy, your brain can't convert fatty acids to fuel. If you eat more fat than your body needs, the extra is stored in fat cells for later use. Fat has more than twice as many calories per gram as carbs and protein, which makes it an efficient form of stored energy. It would take more than 20 pounds of glycogen -- a type of carbohydrate used for fuel -- to store the same amount of energy in just 10 pounds of fat. Your Body Makes Glucose From Carbs Almost all the glucose in your body originated from carbohydrates, which come from the fruit, vegetables, gra
Continue
reading >>

Popular Questions

Doug Freyburger

Others have mentioned the chemical details that lead to limits. That's only one side of the story. The other side is redundancy in energy production. Ketones can be used in anaerobic energy production. It's not as efficient but it is faster. There are times when fast beats efficient so redundancy gets selected for.

Anand R

Acetyl CoA can’t be circulated for two reasons: it’s a high energy compound and it’s labile. So it’s not a stable form for circulation to tissues. Also acetyl coA cannot cross cell membrane.Ketone bodies are an alternate fuel source. More importantly, they are water soluble analogs of fatty acids. This is important since, during starvation there is fat breakdown and excess fatty acids circulate in blood. However, fatty acids cannot be used by brain as fuel since, they cannot cross the blood brain barrier. Liver by producing ketone bodies helps brain cells during starvation.

Also, these ketone bodies, as such, can be used by other tissues as well. There by other tissues refrain from using glucose. Hence, ketone bodies have a glucose-sparing effect. This glucose will be available for tissues like brain and red cells for use.

Barry Gehm

It’s because oxaloacetate is needed to metabolize acetyl-CoA (first step in the Krebs cycle is the reaction of acetyl-CoA with oxaloacetate) and is also needed (and used up) in gluconeogenesis (the production of glucose from amino acids and other small molecules, but NOT from acetyl groups or fatty acids). The liver is primarily responsible for gluconeogenesis, and if it uses up oxaloacetate on that, acetyl-CoA builds up and ties up all the coenzyme A in acetylated form. In order to alleviate this, the liver converts the acetyl-CoA into ketone bodies, and releases them into the blood. These, as the book says, are taken up by other tissues (such as brain and muscle) and converted back into acetyl-CoA. A key point is that these cells can use the acetyl-CoA because they are not depleted in oxaloacetate because they do not carry out gluconeogenesis.

The term “ketone bodies” refers primarily to two compounds: acetoacetate and β‐hydroxy‐butyrate, which are formed from acetyl‐CoA when the supply of TCA‐cycle intermediates is low, such as in periods of prolonged fasting. They can substitute for glucose in skeletal muscle, and, to some extent, in the brain. The first step in ketone body formation is the condensation of two molecules of acetyl‐CoA in a reverse of the thiolase reacti ...

Ketosis is a process that the body does on an everyday basis, regardless of the number of carbs you eat. Your body adapts to what is put in it, processing different types of nutrients into the fuels that it needs. Proteins, fats, and carbs can all be processed for use. Eating a low carb, high fat diet just ramps up this process, which is a normal and safe chemical reaction. When you eat carbohydrate based foods or excess amounts of protein, your ...

Excess ketones are dangerous for someone with diabetes... Low insulin, combined with relatively normal glucagon and epinephrine levels, causes fat to be released from fat cells, which then turns into ketones. Excess formation of ketones is dangerous and is a medical emergency In a person without diabetes, ketone production is the body’s normal adaptation to starvation. Blood sugar levels never get too high, because the production is regulated b ...

If you eat a calorie-restricted diet for several days, you will increase the breakdown of your fat stores. However, many of your tissues cannot convert these fatty acid products directly into ATP, or cellular energy. In addition, glucose is in limited supply and must be reserved for red blood cells -- which can only use glucose for energy -- and brain tissues, which prefer to use glucose. Therefore, your liver converts many of these fatty acids i ...

Sándorné Kincses, Andrea Balláné Kovács (2013) Collectively, β- hydroxybutyric acid, acetoacetic acid and acetone are called ketone bodies. Ketone bodies are created in the body in normal conditions. There are some amino acids (ketogenic amino acids; lysine; leucin) that broke down and their carbon skeleton enters the process of ketogenesis. Large quantity of ketone bodies can be formed in the metabolism of fats. The acetil-CoA is produced ...